Bringing a baby into a marriage that is already troubled isn't usually a good idea, but couples do it all the time. In "Retreat," Martin (Cillian Murphy) and Kate (Thandie Newton) do exactly that, but tragically, the baby is stillborn. The death of their infant only serves to tear them further apart, which helps set up the plot of the film.

The two can't seem to be in the same room without arguing, but they realize that they have a lot of history together and deserve to give their marriage one last shot. They decide to return to a remote Scottish island where they once had a romantic vacation in the hopes of rekindling the fire that they once had. It is a noble plan, until a terrible storm and faulty generator render them without electricity in the cottage. They bicker but manage to make it through the night only to find trouble coming at them as they try to salvage their trip.

The trouble comes in the form of a young man dressed in military fatigues who is washed up on the shore. The soldier has a terrible head wound that really needs medical attention. He introduces himself as Private Jack Coleman (Jamie Bell) from the British Army and claims he is escaping the mayhem in England. He alleges that an airborne flulike virus has taken over much of Europe and could arrive on the island and kill them if they don't take action. This story sets off alarm bells for Kate, who isn't convinced that he is telling the truth. Though Martin has his doubts, he would rather err on the side of caution.

They board themselves up inside the cottage and try to decide what to do next. With a defective generator and no radio communication with the mainland, they are completely isolated. As time wears on, Martin begins to suspect that Jack is not who he claims to be, and Kate's suspicions continue to grow. It doesn't help when Jack begins to act erratically, which puts them in a very dangerous position because they don't know what he is capable of. They must now work together without arguing for the first time in months in order to escape from an increasingly hostile Jack.

Newton and Murphy have excellent chemistry together and are very believable as a couple who are trying to keep their relationship on life support. It is surprising to learn that Jason Isaacs was originally going to play the role of Martin, because after seeing Murphy in the part, it is hard to picture anyone else. That's not to say that Isaacs, a superb actor in his own right, wouldn't have done equally well. It is just hard to imagine another actor being able to exchange such meaningful glances with Newton. When they are in the same room together, they don't even have to exchange words. The audience can just tell by their body language and chemistry that these two have deep-seated issues that can't be worked out with a short island holiday.

The couple's fighting is almost forgotten by the end of the film, because Bell does such an engaging job distracting them as the soldier who may or may not be telling a lie. His performance is so good that viewers probably won't realize that he is the same actor who put on dance shoes to play the troubled young boy in "Billy Elliot." Bell is all grown up now and does a fine job of taking Martin, Kate, and the audience on a psychological roller coaster that doesn't let up until the end of the film.

Carl Tibbetts makes his directorial debut with "Retreat," and shows a lot of potential. Thrillers are not an easy genre, because viewers are fairly savvy and can often guess what happens in the end. A director has to find an unexpected hook on which to hang the film, and Tibbetts does just that. He also makes excellent use of the island background, allowing the blustering Scottish weather to help set the tone and mood of the film. Even as fog rolls in on the couple's first night, the island seems rather large. By the end of the film, nearly every scene feels claustrophobic as the chill from outside and the unknown motives of Jack begin to take an emotional toll on Martin and Kate.

The fact that the film moves from an atmosphere of freedom and hope to a claustrophobic tension is a testament to the screenwriting skills of Tibbetts and fellow writer Janice Hallett. Sometimes a writer can be so immersed in directing his or her own screenplay that it becomes almost impossible to take a step back to detect any potential flaws of the movie being produced. With "Retreat," Tibbetts deftly bypasses this pitfall and produces a truly tense, suspenseful film with the help of three great performances from the lead actors.